Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.71	4.210%	$176.8548	$176.85	$176.85	$176.90
Purchase #2	$89.40	11.147%	$99.3654	$99.37	$99.35	$99.40
Purchase #3	$113.78	3.381%	$117.6269	$117.63	$117.65	$117.60
Purchase #4	$6.94	13.533%	$7.8792	$7.88	$7.90	$7.90
Purchase #5	$146.66	5.315%	$154.455	$154.46	$154.45	$154.50
Purchase #6	$137.73	5.159%	$144.8355	$144.84	$144.85	$144.80
Purchase #7	$178.92	11.455%	$199.4153	$199.42	$199.40	$199.40
7 purchase totals =	$843.14		$900.4321	$900.45	$900.45	$900.50